Solid material comminution or disintegration – Apparatus – Stationary comminuting surface or material bed
Reexamination Certificate
2002-07-25
2004-10-12
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Apparatus
Stationary comminuting surface or material bed
Reexamination Certificate
active
06802466
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of making material, in particular granular or particulate material, collide, with the object of breaking the grains or particles.
BACKGROUND OF THE INVENTION
According to a known technique, material can be broken by subjecting it to an impulse loading. An impulse loading of this kind is created by allowing the material to collide with an impact member, for example a wall, at high speed. It is also possible, in accordance with another option, to allow particles of the material to collide with each other. The impulse loading results in microcracks, which are formed at the location of irregularities in the material. These microcracks continuously spread further under the influence of the impulse loading until, when the impulse loading is sufficiently great or is repeated sufficiently often and quickly, ultimately the material breaks completely and disintegrates into smaller parts. To break the material, it is a precondition that the impact member be composed of harder material than the impacting material; or is at least as hard as the impacting material. The degree of comminution achieved, or breakage probability, increases with the impulse loading. Impact loading always results in deformation and, often considerable, wear of the impact member.
The movement of the material is frequently generated under the influence of centrifugal forces. In this process, the material is centrifugally thrown from a quickly rotating vertical shaft rotor, in order then to collide at high speed with an impact member which is positioned around the rotor. The impact member (impact face) can be formed by a hard metal face (armoured ring), but also by grains or a bed of its own material (autogenous ring). The later case is an autogenous process, and the wear during the impact remains limited. It is also possible to make the particles collide with an impact member that co-rotates with the rotor at a greater radial distance than the location from where the particles are centrifugally thrown.
The impulse forces generated in the process are directly related to the velocity at which the material leaves the rotor and strikes against the stationary or co-rotating impact member. In other words, the more quickly the rotor rotates in a specific configuration, the better the breaking result will be. Furthermore, the angle at which the material strikes the impact member has an effect on the breaking probability. The same applies to the number of impacts which the material undergoes or has to deal with and how quickly in succession these impacts take place.
A distinction can be drawn between single impact crushers, in which the material is loaded by a single impact, indirect double impact crushers, in which the material is accelerated again after the first impact and loaded by a second impact, which process can be repeated further, and direct double impact crushers, in which the material is loaded in immediate succession by two or more impacts which can be achieved by throwing the material against the co-rotating impact member: Direct double impact is normally preferred, since this considerably increases breakage probability, because during co-rotating impact the particles are simultaneously loaded and accelerated for direct successive secondary impact, with secondary impact velocity exceeding primary impact velocity; while energy consumption is virtually similar to single impact (indirect double impact doubles energy consumption).
In the known single impact crushers, the impact faces, which form an armoured ring around the rotor, are generally disposed in such a manner that the impact (stone-on-steel) in the horizontal plane as far as possible takes place perpendicularly. The specific arrangement of the impact faces which is required for this purpose means that the armoured ring as a whole has a type of knurled shape with numerous projecting corners. A device of this kind is known from U.S. Pat. No. 5,248,101. In the known method impact is heavily disturbed by the projecting corners which affects up to two-thirds of the particles. This causes wear rate along the armoured ring to be extremely high, while breaking probability is reduced significantly. Unfortunately, remaining elastic energy (rebound velocity) cannot be used to produce direct double impact because it is virtually impossible to locate secondary impact plates in an effective position. Only single impact can therefore be achieved. The centrifugal acceleration phase which does not contribute to the loading of the particle, but causes heavy wear along the impeller blade which is a major cause of concern with these type of crushers.
Instead of a stationary armoured ring a stationary trough structure may be disposed around the edge of the rotor, in which trough an autogenous bed, or autogenous ring, of the same material builds up. The centrifugally thrown material then strikes (stone-on-stone) the autogenous ring. A device of this kind is known from EP 0 074 771. The level of comminution of the known method is however limited, and the crusher is primarily employed for the after-treatment of granular material by means of rubbing the grains together, and in particular for “cubing” irregularly shaped grains. U.S. Pat. No. 4,575,014 has disclosed a device with an autogenous rotor blade, from which the material is centrifugally thrown against an armoured ring (stone-on-steel) or a bed of the same material (stone-on-stone).
U.S. Pat. No. 5,863,006 discloses a method for simultaneously loading and accelerating material that is metered on a horizontally disposed meter face which rotates about a vertical axis of rotation; this meter face is however separately supported on bearings and is as a whole carried by a vertical shaft which also carries a cylindrical rotor which wall is positioned concentrically around the meter face. Because of the separate bearing the meter face rotates at a lower velocity than the rotor. The material is supposed to be centrifugally thrown from this meter face and to collide with the wall of the rotor, which rotates at a much higher peripheral velocity than the meter face; and to build up an autogenous wall of own material, that acts as a co-rotating autogenous ring. This way co-rotating autogenous impact is supposed to take place with a high (relative) velocity, while wear is limited to a minimum. The material is then led to leave the rotor via ports in the wall and is then thrown against a stationary autogenous ring which is situated around the rotor for secondary autogenous impact. The comminution intensity during primary impact is however limited because the material is actually “floating freely” from the meter face (the material does not feel this rotating face) towards the co-rotating autogenous impact face, along which trajectory the particles are gradually accelerated and taken up in the autogenous ring. The intended level of impact does not materialize. Moreover, it is very difficult to keep a rotor, containing such “huge” autogenous ring, in balance; this requires special measures to be taken, which are described in U.S. Pat. No. 5,863,006 and makes the construction extremely complicated. The known method does not essentially differ from the method disclosed in DE 31 16 159.
A much better level of comminution intensity and comminution efficiency is obtained with a known method for direct successive double impact generated by a co-rotating impact member, which is disclosed U.S. Pat. No. 5,860,605 and is in the name of applicant. This known method, the synchrocrusher, features the synchroprinciple which allows for simple design, utilization of the principle of relativity, universal synchronization and above all provides fully deterministic behaviour. The material is metered on a meter face, central on the rotor, and from there taken up by guide members which are positioned around the meter face and are relatively short and preferably aligned backwards. From these guide members the material is centrifugally thrown, with a relative low take off velocity, into the direction of
Rosenbaum Mark
Van Der Zanden Rosemarie Johanna
Young & Thompson
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