Solid material comminution or disintegration – Apparatus – Including means applying fluid to material
Reexamination Certificate
1999-10-20
2002-08-13
Ostrager, Allen (Department: 3725)
Solid material comminution or disintegration
Apparatus
Including means applying fluid to material
C241S086100, C241S186300, C241S248000
Reexamination Certificate
active
06431477
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a gas-flow type chipping machine with a rotating beater-wheel system and a method for optimizing such chipping machines.
A consequence of the constantly growing demand for wood chips to be used, for examples in manufacturing chip board, which is being voiced by the wood-processing industry, is that ever larger machines with greater throughput capacities are being built to produce the starting materials that are required to satisfy this demand. Recently, old wood that has been recovered by recycling has been used as the raw material for manufacturing wood chips. These developments are causing various problems that have been overcome with the aid of the present invention.
On the one hand, depending on the purpose for which it was previously used, old wood can contain a comparatively large quantity of impurities. In the case of construction lumber, these impurities are frequently in the form of traces of concrete and sand that have adhered to be wood, as well as nails and screws. DE 43 16 350 describes an effective way of removing such impurities from the feed material. To this end, an input apparatus in the form of a wind sifter is incorporated ahead of a chipping device. The feed material, previously cleaned by a magnetic drum and a sieve surface, is passed through a sifting channel in which relatively heavy particles are separated out. The transverse flow of air that performs the actual sifting also serves as the motive force that moves the feed material through a wide channel into the chipping area of the chipping machine. Chipping machines that are configured in this way achieve a high level of separation of foreign matter and deliver good chip quality, always providing that the material is sufficiently homogeneous with respect to size and density.
This cannot always be assured when old wood is reused, when different types of wood of various densities are mixed so that the chipping knives that extend to the full depth of the chipping area are not acted upon uniformly to their total length. Rather, there are zones in which the more material collects, with the result that more chipping work has to be done. The result is greatly increased localized wear that leads to the need for premature replacement of the blades and thus to shorter machine run times.
This undesirable effect is also exacerbated by the design of powerful machines with deeper chipping areas, in which it is, of course, more difficult to ensure that the length of the blades can be acted upon uniformly because they are so long.
Certainly, DE-OS 224 37 202 and DE-PS 26 01 384 describe measures to ensure that the blades are acted upon in a uniform manner. However, because of the fundamentally different ways of delivering the feed material into the chipping area, these cannot of necessity be transferred to the present invention. In the cases of both OS 24 37 202 and DE-PS 26 01 384, the Reed material passes through an inclined entry chute by gravity, and then enters the chipping area at its centre. In the case of OS 24 37 202, the entry chute is divided into a plurality of tracks that extend to varying distances into the interior of the chipping area. At the end of each track there is an impact plate that diverts the flow of material to the chipping tools into a radial direction. Because of the arrangement of the impact plate, which are staggered to the depth of the chipping area, the material is distributed evenly to the depth of the chipping area.
In the case of DE-OS 26 01 384, at its machine end, the fixed entry chute becomes a rotating truncated cone within which there is a similarly rotating distributing device. The distributing device consists essentially of three circular sectors that are staggered to the depth of the chipping area and are separated by bulkheads; diametrically opposed cutouts in the outer surface of the truncated cone are associated with these circular sectors. The feed material is delivered to specific areas of the chipping tools through the cutouts in the outer surface.
It is true that these known devices that ensure that the chipping tools are acted upon evenly to the whole length function work well in the case of chipping machines with an entry for the material by way of a chute, and if the feed material is homogeneous; however, as a result of design and construction constraints they cannot be used in conjunction with a chipping machine that has a pneumatic charging system that is preferably combined with a previous wind-sifting system. Whereas the entry chute controls the feed material at low speeds and guides it to a predetermined point in the chipping area, in the case of pneumatic charging that is effected with the aid of the flow of air, the feed material is injected into the chipping area at high speed. Measures that belong to the prior art cannot accommodate the feed material that arrives with a great deal of kinetic energy from a predetermined direction, and then deliver it to the chipping tools.
SUMMARY OF THE INVENTION
Against this background, it is the objective of the present invention to describe a gas-flow type chipping machine in which the charging is effected pneumatically and in which the chipping tools are acted upon uniformly to their whole length.
According to the present invention, this objective has been achieved by a chipping machine, wherein, in order to ensure that the feed material is evenly distributed to the length of the chipper tools, there are at least two impact surfaces that are arranged in the chipping area so as to be axially staggered by depth, the impact surface that follows in the axial direction of delivery projecting beyond the axial projection of the preceding impact surface.
It is a further objective of the present invention to describe a method for optimizing the position and dimensions of the impact surfaces according to the present invention.
This objective has been achieved by a method with the following steps: a) the wear on the chipping tools at specific positions prior to operation is determined; b) the machine is operated for a specific amount of time; c) the wear on the chipping tools at the places identified in a) is determined; the diameter and/or spacing of the impact surfaces is varied in the event that the wear on the chipping tools is not constant at the locations identified in a); the steps a) to d) are repeated until such time as the wear on the chipping tools is constant at the locations identified in a).
According to the present invention, the feed material is deflected radially on impact surfaces that are arranged at different depths, as a function of the eccentricity of the projections on which the feed material moves into the chipping machine. In this way, a radial material track can be associated with each axial trajectory, each of said tracks leading to one specific sector of the drum-like chipping track. Only by creating conditions that are so defined can the way in which the chipping tools are acted upon to their whole length be controlled by changing parameters such as the position and/or dimensions of the impact surfaces. Because of this it is possible to introduce inhomogeneous material into a chipping machine according to the present invention, or increase the depth of the chipping area in order to increase the throughput rate. Although—in the past—this resulted in great costs because of locally increased wear on the chipping tools, now the chipping tools themselves are worn evenly to their whole lengths under such conditions, so that the interval between tool changes have become longer, and machine run time is correspondingly longer, with the result that overall economy has been enhanced.
The chipping machines according to the present invention are particularly advantageous in the case of new investment. Because of the specific and even distribution of the feed material to the whole depth of the chipping area, the present invention makes it possible to build chipping machines of large dimensions with deep chipping areas. This means that machines that are n
Hong William
Kueffner Friedrich
Ostrager Allen
Pallmann Maschinenfabrik GmbH & Co. KG
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