Solid material comminution or disintegration – Processes – By utilizing kinetic energy of projected or suspended material
Reexamination Certificate
2002-03-22
2004-09-07
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
By utilizing kinetic energy of projected or suspended material
C241S275000
Reexamination Certificate
active
06786436
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of the acceleration of material, in particular a stream of granular or particulate material, with the aid of centrifugal force, with, in particular, the aim of causing the accelerated grains or particles to collide at a speed such that they break.
According to a known technique the movement of a stream of material can be accelerated with the aid of centrifugal force. With this technique the material is introduced into the central chamber of a rotor and is then picked up by guide elements which are arranged around the central chamber and are supported by the rotor. Normally such a rotor rotates about a vertical axis of rotation; however, rotation can also take place about a horizontal axis. The material is accelerated along the guide elements and propelled outwards at high speed and at a certain angle of flight. The angle of flight is usually barely affected by the speed of rotation and is virtually constant for the individual grains in a granular stream. The speed which the material acquires during this operation is determined by the speed of rotation of the rotor. The speed of flight is composed of a radial speed component and a speed component oriented perpendicularly to the radial, or transverse speed component.
Viewed from the stationary standpoint and when the influence of air resistance and air movements are disregarded, the material moves at virtually constant speed along a virtually straight stream after it has left the guide element. This straight stream is directed forwards, viewed in the direction of rotation, and the magnitude of the angle of flight is in this case determined by the magnitudes of the radial and transverse speed components which, in turn, are determined by the length and positioning of the guide element and the coefficient of friction. If the radial and transverse components are identical, the angle of flight is 45°.
Viewed from a standpoint moving with the guide element, the material moves in a spiral stream after it leaves the guide element, which spiral stream is oriented backwards, viewed in the direction of rotation, and is in the extension of the guide element. In this case the relative speed increases as the material moves further away from the axis of rotation.
The material can be propelled outwards in this way, with the aim of distributing or spreading it regularly; for example salt on a road or seed over agricultural land.
The material can also be collected by a stationary impact element that is arranged in the straight stream which the material describes, with the aim of causing the material to break during impact. The stationary impact element can be formed, for example, by an armoured ring which is arranged around the rotor. The comminution process takes place during this single impact, the equipment being referred to as a single impact breaker.
Research has shown that for the comminution of material by means of impact stress a perpendicular impact is not optimum for the majority of materials and that, depending on the specific type of material, a higher probability of break can be achieved with an impact angle of approximately 75°, or at least between 70° and 85°. Furthermore, the probability of break can also be appreciably increased if the material to be broken is exposed not to single impact stress but to multiple, or at least double, impact stress in rapid succession. What is most important, however, is that the impact or impacts as far as possible take place free from interference.
Such a multiple impact can be achieved by, instead of allowing the material to impinge directly on a stationary impact element, first allowing the material to collide with an impact element that is moving with the guide element, that is rotating at the same speed, in the same direction and around the same axis of rotation, but at a greater radial distance from the axis of rotation than the guide element and is arranged transversely in the spiral stream which the material describes. Because the impact takes place essentially deterministically, the impact surface can be arranged at an angle such that the impact takes place at an optimum angle. The material is simultaneously stressed and additionally accelerated by the impact on the moving impact element before it impinges on the stationary collision element. With this arrangement both the acceleration and the impact take place in two steps, this equipment being referred to as a direct multiple impact breaker. With this arrangement it is possible then to allow the material to impinge on a further moving impact element which is arranged an even greater distance away from the axis of rotation.
It is thus possible to bring material into motion with the aid of centrifugal force and then to subject it to single or multiple stress in various ways.
BACKGROUND TO THE INVENTION
The invention described here relates to a rotor which rotates about an axis of rotation, by means of which material, in particular a stream of granular material, is accelerated with the aid of a guide element that is supported by the rotor, with the aim, in particular, of allowing the material to collide at such a speed that the material breaks. The rotor described here can be arranged in a comminution installation, for example a breaker or a mill, but can also be arranged in a distributor or spreader device.
In the known single impact breakers the impact surfaces of the stationary impact element are in general so arranged that the impact with the horizontal surface takes place perpendicularly as far as possible. The consequence of the specific arrangement of the impact surfaces necessary for this is that the armoured ring as a whole has a sort of knurled shape. Such an installation, which is equipped with a rotor which rotates about a vertical axis of rotation, is disclosed in U.S. Pat. No. 5,921,484.
PCT/NL 97/00 565, which has been drawn up in the name of the Applicant, discloses a method and installation for a direct multiple impact breaker which is equipped with a rotor which rotates about a vertical axis of rotation, by means of which the material is accelerated in two steps, these being, respectively, guiding over a relatively short guide element and impact by a moving impact element, in order then to be allowed to impinge on a stationary impact element in the form of individual evolvent impact elements which are arranged around the rotor. Stressing thus takes place in two immediately successive steps. The second impact takes place at a speed, or kinetic energy, which remains after the first impact, that is to say without additional energy having to be supplied. This residual speed is usually at least equal to the speed at which the first impact takes place. The stationary collision element can comprise an armoured ring or a bed of own material, whilst some of the material can be guided along the stationary collision elements bypassing the rotor.
U.S. Pat. No. 4,083,504 (Wattles et al.) discloses an apparatus with a rotor rotating about a vertical axis of rotation where the material is metered on the rotor with two upstanding chutes which are a distance away from the axis of rotation. This makes it possible to support the rotor with a shaft which is mounted on top of the rotor between the chutes; which results in a rotor which is hanging free above the hopper. As a whole this results in a more compact construction and makes the axis and drive and rotor more easily accessible. A problem is that the material has to be fed to the rotor a distance away from the axis of rotation because the shaft is in the middle. To obtain a reasonable regular distribution of the material to the rotor, in such a way that the material is spread all around the rotor to be accelerated and to impact against the circular series of depending fixed impactors that are positioned around the rotor, the material is fed to the rotor through at least two chutes which are mounted opposite of each other, and the bottom of these chutes are preferably directed angled towards the axis of rotation and attached to a
Rosenbaum Mark
van der Zanden Rosemarie Johanna
Young & Thompson
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